The present invention relates to high strength aluminum alloy products such as vehicular panels and other structural members useful in general and sporting goods applications and to improved methods for producing the same. In general, heat treatable aluminum alloys have been employed in a number of applications involving relatively high strength such as vehicular members, sporting goods and other applications. Aluminum Alloys 6061 and 6063 are among the largest selling, if not the largest selling, heat treatable alloys in the United States, with 6061 alloy being provided for sheet, plate and forging applications, and Alloy 6063 being provided for extrusions. The sales limits for these alloy compositions are:
TABLE I ______________________________________ Alloy Si Mg Cu Cr Mn Fe Zn ______________________________________ 6061 .4-.8 .8-1.2 .15-.40 .04-.35 .15 .7 .25 max. max. max. 6063 .2-.6 .45-.9 .10 .10 .10 .35 .10 max. max. max. max. max. ______________________________________
Alloy 6261 is generally similar in sales limits to the 6061 sales limits indicated above, except that it contains 0.2-0.35% Mn and limits Cr to 0.10% max. as an impurity. As in most aluminum alloys, the actual manufacturing limits for composition are typically narrower than the sales limits. These heat treatable 6XXX type alloys are well known for their useful strength and toughness properties in both T4 and T6 tempers and are generally considered as having relatively good corrosion resistance which makes them advantageous even over the very high strength and more expensive 7XXX alloys which sometimes can exhibit more corrosion than 6XXX alloys. Typical properties for these alloys in the longitudinal direction, including yield strength (YS), tensile strength (TS) and elongation (EL) for both the T4 and T6 tempers are as follows:
TABLE II ______________________________________ Alloy YS TS EL % ______________________________________ T4 TEMPER 6061 21 35 22 6063 13 25 22 T6 TEMPER 6061 40 45 12 6063 31 35 12 ______________________________________
As is known, the T4 condition refers to a solution heat treated and quenched condition naturally aged to a substantially stable property level, whereas the T5 and T6 tempers refer to a stronger condition produced by artificially aging at typical temperatures of 220.degree.-350.degree. or 400.degree. F. for a typical period of hours.
Recently, Alloys 6009 and 6010 have been used as vehicular panels in cars, boats, and the like. These alloys and products thereof are described in U.S. Pat. No. 4,082,578, issued Apr. 4, 1978 to Evancho et al. Alloy 6010 sales limits are 0.8 to 1.2% Si, 0.6 to 1% Mg, 0.15 to 0.6% Cu, 0.2 to 0.8% Mn, balance essentially aluminum, and Alloy 6010 generally conforms to Alloy Type I in said U.S. Pat. No. 4,082,578. Alloy 6009 sales limits are the same except for lower Si at 0.6 to 1% and lower Mg at 0.4 to 0.6%, and Alloy 6009 generally conforms to Alloy Type II in said U.S. Pat. No. 4,082,578. In spite of the usefulness of the aforementioned alloys, there exists room for improvement, especially in the areas of strength, toughness and impact and dent resistance. Adding more strengthening elements such as copper, manganese, magnesium, or silicon or zinc has been suggested from time to time, but it is recognized that such can introduce more problems in corrosion performance, manufacture or other areas. For instance, adding substantial amounts of copper to the above-mentioned alloys would be considered to seriously impair corrosion and other performance aspects. One such alloy, Alloy 6066, is heavily loaded with supposedly strengthening elements such as copper and manganese, yet is seriously lacking in toughness and impact properties so as to be seriously impaired for use in structural applications requiring durability.
The present invention provides for improved products in sheet, plate, extruded and other forms utilizing a single aluminum alloy produced as herein provided and which solves various problems, including improved strength over 6061 and 6063 type alloys and improved impact and dent resistance and toughness over the newer 6009 and 6010 type alloys, together with other advantages in more stable aging response and still more advantages as will appear hereinbelow.